Metabolic inflammatory volume and total inflammatory glycolysis: novel parameters to evaluate PET-CT disease activity in Takayasu arteritis

Objectives To evaluate diagnostic accuracy for active Takayasu arteritis (TAK) for two novel F-18-fluorodeoxyglucose PET-CT parameters, the inflammatory volume (MIV) and total inflammatory glycolysis (TIG), to quantitate volume of metabolically-active arterial tissue. Methods From a cohort of TAK (n = 36, 35 immunosuppressive-naive), images of PET-CTs were reviewed for mean and maximum standardized uptake value (SUVmean and SUVmax), target-to-blood pool ratio (TBR), target-to-liver ratio (TLR), and PET Vasculitis Activity Score (PETVAS). Regions of interest were drawn to semiautomatically calculate MIV in areas of F-18-fluorodeoxyglucose uptake >= 1.5 SUVmean after excluding physiological tracer uptake. TIG was calculated by multiplying MIV with SUVmean. PET-CT parameters, ESR, CRP, and clinical disease activity scores were compared against the gold standard of physician global assessment of disease activity (PGA, active/inactive). Results Using dichotomized cut-offs for active TAK at SUVmax (>= 2.21), SUVmean (>= 1.58), TBR (>= 2.31), TLR (>= 1.22), PETVAS (various cut-offs), ESR (>= 40 mm/hour), and CRP (>= 6 mg/L), the novel indices MIV (>= 1.8) and TIG (>= 2.7) performed similar [area under the receiver operating characteristics curve (AUC) 0.873 for both] to SUVmax (AUC 0.841) and SUVmean (AUC 0.851), and better than TBR (AUC 0.773), TLR (AUC 0.773), PETVAS [>= 5.5 (AUC 0.750), >= 10 (AUC 0.636), >= 15 (AUC 0.546)], ESR (AUC 0.748), or CRP (AUC 0.731). MIV and TIG had similar agreement with PGA or CRP as with SUVmax or SUVmean, and better agreement than TBR, TLR, or PETVAS cut-offs. Conclusions MIV and TIG performed similarly, therefore, are viable alternatives to existing PET-CT parameters to assess TAK disease activity in this preliminary report.

Automated summary

This study evaluates the diagnostic accuracy of two novel F-18-fluorodeoxyglucose PET-CT parameters, the inflammatory volume (MIV) and total inflammatory glycolysis (TIG), for assessing active Takayasu arteritis (TAK). The results show that MIV and TIG perform similarly to existing PET-CT parameters and can be used to evaluate disease activity in TAK.